Water-soluble phenylenediamine compositions and methods for stabilizing ethylenically unsaturated compounds and monomers

ABSTRACT

Compositions and methods for inhibiting polymerization of ethylenically unsaturated monomers are provided. The compositions include a water-soluble phenylenediamine composition.

FIELD OF THE INVENTION

The present invention relates to water-soluble phenylenediaminecompositions and methods for inhibiting polymerization of ethylenicallyunsaturated hydrocarbons.

BACKGROUND OF THE RELATED TECHNOLOGY

During the refining process, hydrocarbon streams are frequently exposedto elevated temperatures, which can lead to premature polymerization ofthe desired monomer. The premature polymerization results in reductionof the amount of the desired monomer end-products as well as a loss inefficiency caused by fouling and deposit formation within the processingequipment.

In order to reduce or prevent polymer formation, stabilizing orinhibitor compositions have been introduced into the hydrocarbon streamat or upstream of a location where polymerization is likely to occur,such as where distillation is performed.

Phenylenediamines (PDA's) are widely used as antioxidants andpolymerization inhibitors. However, their use is limited to hydrocarbonstreams where the PDA is soluble. A number of patents relate to the useof various PDA's, combinations of different PDA's and combinations ofPDA's with other inhibitors to stabilize hydrocarbon fluids.

Among these patents is U.S. Pat. No. 6,200,461 to Eldin which describesmethods and compositions for inhibiting the polymerization ofethylenically unsaturated hydrocarbons under both processing and storageconditions by the addition of combinations of aminophenol compounds andeither PDA or hydroxylamine. Other combinations have also been used.These include inhibitor combinations containing a PDA with an oximecompound and a hydroxylamine as shown in U.S. Pat. No. 5,489,718 toArhancet. Other examples include the combination of a PDA and ahydroxylamine as shown in U.S. Pat. No. 5,396,004 to Arhancet and a PDAwith a hydroxytoluene compound as shown In U.S. Pat. No. 5,416,258 toArhancet et al.

Examples of specific PDA compounds may be found in U.S. Pat. No.4,929,778 to Roling which describes compositions including a PDAcompound which has at least one N—H bond and a hindered phenol usefulfor inhibiting the polymerization of styrene during elevated temperatureprocessing, storage and shipment. U.S. Pat. No. 4,774,374 to Abruscatoet al. discloses an oxygenated species formed by the reaction of oxygenand an N-aryl-N′-alkyl-p-phenylenediaminie.

While each of these references provides compositions and methods thatreduce premature polymerization of ethylenically unsaturated monomers,they are generally limited to hydrocarbon processing and storage wherethey are soluble, which does not include where water is present.Therefore, the currently available PDA inhibitors do not adequatelyaddress the concerns of the prevention of premature polymerization of amonomers with water-solubility, where a water phase is present.

Therefore, it would be desirable to provide a water-soluble compositionfor the reducing and or preventing the polymerization of ethylenicallyunsaturated monomers. Desirably, the composition will include awater-soluble phenylenediaminie composition which acts as anantioxidant/free-radical polymerization inhibitor.

SUMMARY OF THE INVENTION

The present invention provides a water-soluble phenylenediaminecomposition which also functions as an antioxidant/free-radicalpolymerization inhibitor. The compounds are of the following formula:

wherein at least one of R¹, R², and R³ is

R¹, R² and R³ are independently selected from H, alkyl, hydroxyalkyl,—O—R⁶, —S—R⁶, —C(O)R⁶, —C(S)R⁶, —N—(R⁷)(R⁸), aryl, and

R⁵ is selected from the group consisting of H, alkyl, hydroxyalkyl, O,S, —O—R⁶, —S—R⁶, —N—(R⁷)(R⁶), and aryl;

Z comprises one or more substituents selected from the group consistingof hydrogen, alkyl, alkenyl, alkynyl, cycloalkyl, cycloalkenyl, aryl,heterocyclo, —CN, —NO₂, —O—R⁶, —S—R⁶, and —N—(R⁷)(R⁸); and

R⁶, R⁷ and R⁸ are independently selected from the group consisting ofhydrogen, alkyl, alkenyl, alkynyl, cycloalkyl, cycloalkenyl, aryl andheterocyclo. Desirably, the compound corresponds the following formula:

The compounds of formula (I), above, may be added to a compositionincluding an ethylenically unsaturated monomer to produce a compositionresistant to polymerization. The addition of the water-solublephenylenediamine composition of the present invention to the monomercomposition may occur during synthesis or processing or storage of thecomposition.

The compounds of the present invention include a reaction product of aphenylenediamine compound of the following formula:

wherein at least one of R¹, R² and R³ is H.

R¹, R² and R³ are independently selected from the group consisting of,alkyl, hydroxyalkyl, —O—R⁶, —S—R⁶, —C(O)R⁶, —C(S)R⁶, —N—(R⁷)(R⁸), andaryl;

Z comprises one or more substituents selected from the group consistingof hydrogen, alkyl, alkenyl, alkynyl, cycloalkyl, cycloalkenyl, aryl,heterocyclo, —CN₁—NO₂, —O—R⁶, —S—R⁶, and —N(R⁷)(R⁸); and

R⁶, R⁷ and R⁸ are independently selected from the group consisting ofhydrogen, alkyl, alkenyl, alkynyl, cycloalkyl, cycloalkenyl, aryl andheterocyclo,

with a heterocylic compound of the following formula:

wherein R⁵ is selected from the group consisting of H, alkyl,hydroxyalkyl, —O—R⁶, —S—R⁶, —N—(R⁷)(R⁸), and aryl.

Another aspect of the present invention provides a method of preparing awater-soluble phenylenediamine composition including the step ofreacting a phenylenediamine compound of the following formula:

wherein at least one of R¹, R² and R³ is H and

R¹, R² and R³ are independently selected from the group consisting of,alkyl, hydroxyalkyl, —O—R⁶, —S—R⁶, —C(O)R⁶, —C(S)R⁶, —N—(R⁷)(R⁸), andaryl;

Z comprises one or more substituents selected from the group consistingof hydrogen, alkyl, alkenyl, alkynyl, cycloalkyl, cycloalkenyl, aryl,heterocyclo, —CN, —NO₂, —O—R⁶, —S—R⁶, and —N(R⁷)(R⁸); and

R⁶, R⁷ and R⁸ are independently selected from the group consisting ofhydrogen, alkyl, alkenyl, alkynyl, cycloalkyl, cycloalkenyl, aryl andheterocyclo,

with a heterocylic compound of the following formula:

wherein R⁵ is selected from the group consisting of H, alkyl,hydroxyalkyl, —O—R⁶, —S—R⁶, —N—(R⁷)(R⁸), and aryl. Desirably, thephenylenediamine compound is 1,4-phenylenediamine.

A further aspect of the present invention provides a method of reducingor inhibiting fouling and deposit formation during hydrocarbonprocessing including the step of administering an effective amount ofone or more water-soluble compounds of the following formula to ahydrocarbon stream at or upstream of a location where said foulingand/or said deposit formation may occur:

wherein at least one of R¹, R², and R³ is

R¹, R² and R³ are independently selected from H, C₁-C₁₈ alkyl,hydroxyalkyl, —O—R⁶, —S—R⁶, —N—(R⁷)(R⁸), aryl, and

R⁵ is selected from the group consisting of H, alkyl, hydroxyalkyl,—O—R⁶, —S—R⁶, —N—(R⁷)(R⁸), and aryl;

Z comprises one or more substituents selected from the group consistingof hydrogen, alkyl, alkenyl, alkynyl, cycloalkyl, cycloalkenyl, aryl,heterocyclo, —CN, —NO₂, —O—R⁶, —S—R⁶, and —N(R⁷)(R⁸);

R⁶, R⁷ and R⁸ are independently selected form the group consisting ofhydrogen, alkyl, alkenyl, alkynyl, cycloalkyl, cycloalkenyl, aryl andheterocyclo; and wherein

said composition is water-soluble

DETAILED DESCRIPTION OF THE INVENTION

The present invention includes compounds of the formula:

wherein the NHR³ group may be present in any of the ortho, para, andmeta positions,

at least one of R¹, R², and R³ is

R¹, R² and R³ are independently selected from H, alkyl, hydroxyalkyl,—O—R⁶, —S—R⁶, —C(O)R⁶, —C(S)R⁶, —N—(R⁷)(R⁸), aryl, and

R⁵ is selected from the group consisting of H, alkyl, hydroxyalkyl, O,S, —O—R⁶, —S—R⁶, —N—(R⁷)(R⁸), and aryl;

Z comprises one or more substituents selected from the group consistingof hydrogen, alkyl, alkenyl, alkynyl, cycloalkyl, cycloalkenyl, aryl,heterocyclo, —CN, —NO₂, —O—R⁶, —S—R⁶, and —N(R⁷)(R⁶); and

R⁶, R⁷ and R⁸ are independently selected from the group consisting ofhydrogen, alkyl, alkenyl, alkynyl, cycloalkyl, cycloalkenyl, aryl andheterocyclo. Desirably, the second amine group is in the para position,corresponding to the following formula:

The term “alkyl” is meant to include substituted or unsubstituted,straight or branched chain saturated hydrocarbon groups, desirablyhaving 1 to 20 carbons in the main chain. Examples of unsubstitutedgroups include methyl, ethyl, propyl, isopropyl, n-butyl, t butyl,isobutyl, pentyl, hexyl, isohexyl, heptyl, 4,4-dimethyl pentyl, octyl,2,2,4-trimethylpentyl, nonyl, decyl, undecyl, dodecyl, and the like.Substituents may include halogen, hydroxy, or aryl groups.

The term “hydroxyalkyl” is meant to include an alkyl group as describedabove with at least one hydroxy group substituent.

The term “alkenyl” is meant to include substituted or unsubstituted,straight or branched chain hydrocarbon groups including at least onecarbon to carbon double bond in the chain, and desirably including 2 to10 carbons in the normal chain. Examples of such unsubstituted alkenylgroups include ethenyl, propenyl, isobutenyl, butenyl, pentenyl,hexenyl, heptenyl, octenyl, nonenyl, decenyl, and the like. Substituentsmay include those as described above.

The term “alkynyl”, is meant to include substituted or unsubstituted,straight and branched chain hydrocarbon groups including at least onecarbon to carbon triple bond in the chain, and preferably having 2 to 10carbons in the normal chain. Examples of such unsubstituted groupsinclude ethynyl, propynyl, butynyl, pentynyl, hexynyl, heptynyl,octynyl, nonynyl, decynyl, and the like. Substituents may include thoseas described above.

The term “cycloalkyl” is meant to include substituted or unsubstituted,saturated cyclic hydrocarbon ring systems, preferably containing 1 to 3rings and 3 to 7 carbons per ring. Exemplary unsubstituted such groupsinclude cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl,cyclooctyl, cyclodecyl, cyclododecyl, and adamantyl. Exemplarysubstituents include one or more alkyl groups as described above, or oneor more groups described above as alkyl substituents.

The term “cycloalkenyl” is meant to include hydrocarbon ring systemswhich may be substituted or unsubstituted as described above forcycloalkyl, further containing at least one carbon to carbon double bondforming a partially unsaturated ring. These may also includesubstituents as described above.

The terms “heterocyclo” or “heterocyclic” are meant to includesubstituted or unsubstituted, fully saturated or unsaturated, aromaticor non-aromatic cyclic groups having at least one heteroatom (such as N,O, and S) in at least one ring, desirably monocyclic or bicyclic groupshaving 3-6 atoms in each ring. The heterocyclo group may be bondedthrough any carbon or heteroatom of the ring system. Examples ofheterocyclic groups include, without limitation, thienyl, furyl,pyrrolyl, pyridyl, imidazolyl, pyrrolidinyl, piperidinyl, azepinyl,indolyl, isoindolyl, quinolinyl, isoquinolinyl, benzothiazolyl,benzoxazolyl, benzimidazolyl, benzoxadiazolyl, and benzofurazanyl. Thesemay also include substituents as described above.

The term “aryl” is meant to include substituted or unsubstitutedmonocyclic, bicyclic or tricyclic aromatic groups, desirably includingone or two rings which contain only carbon ring atoms and 6 to 12 ringcarbons. The term “aryl” can also refer to an aryl group fused to amonocyclic cycloalkyl or monocyclic heterocycle in which the point(s) ofattachment is/are on the aromatic portion. Examples of aryl groupsinclude phenyl, biphenyl, and naphthyl. Aryl rings fused to cycloalkylsare include indanyl, indenyl, and tetrahydronaphthyl. Examples of arylgroups fused to heterocyclic groups include 2,3-dihydrobenzofuranyl,benzopyranyl, 1,4-benzodioxanyl, and the like. Substituents may includethose as described above as well as nitro groups.

The water-soluble phenylenediamine compounds of the present inventionmay be formed by the reaction of a phenylenediamine compound of thefollowing formula:

wherein at least one of R¹, R² and R³ is H;

R¹, R² and R³ are independently selected from the group consisting of,alkyl, hydroxyalkyl, —O—R⁶, —S—R⁶, —C(O)R⁶, —C(S)R⁶, —N—(R⁷)(R⁸), andaryl;

Z comprises one or more substituents selected from the group consistingof hydrogen, alkyl, alkenyl, alkynyl, cycloalkyl, cycloalkenyl, aryl,heterocyclo, —CN, —NO₂, —O—R⁶, —S—R⁶, and —N(R⁷)(R⁸); and

R⁶, R⁷ and R⁸ are independently selected from the group consisting ofhydrogen, alkyl, alkenyl, alkynyl, cycloalkyl, cycloalkenyl, aryl andheterocyclo,

with a heterocylic compound of the following formula:

wherein R⁵ is selected from the group consisting of H, alkyl,hydroxyalkyl, —O—R⁶, —S—R⁶, —N—(R⁷)(R⁸), and aryl. Desirably, theheterocyclic compound is propylene oxide or butylene oxide

This reaction produces a mixture of reaction products that may beseparated by any of a variety of means known in the art, includingchromatography. For example, the reaction of 1,4-phenylenediamine withthe substituted heterocyclic compound may produce a mixture of fivedifferent products as shown in the following reaction scheme:

Similarly, where the phenylenediamine staring material includes anon-hydrogen substitution, the products of the reaction with thesubstituted heterocyclic compound are shown by the reaction scheme asshown below.

The reaction of 1,4-phenylenediamine with propylene oxide will alsoproduce a mixture of products which includeN,N′-dihydroxypropylphenylenediamine,N,N-dihydroxypropylphenylenediamine, N-hydroxypropylphenylenediamine,N,N,N′-trihydroxypropylphlenylenediamine, andN,N,N′,N′-tetrahydryoxypropylphenylenediamine.

The phenylenediamine compounds of the present invention are useful asantioxidant/free-radical polymerization inhibitors. In other words, theyare useful to stabilize hydrocarbon compositions including ethylenicallyunsaturated monomers by inhibiting polymerization. They are useful asinhibitors under both process and storage conditions including where themonomers are subjected to elevated temperatures, for example up to about125° C.

The water-soluble phenylenediamine compositions are useful with avariety of ethylenically unsaturated monomers. These include, but arenot limited to vinyl aromatic compounds such as styrene, substitutedstyrene, divinylbenzene, vinyl toluene, and vinyl naphthalene, and otherethylenically unsaturated monomers such as acrylic acid, alkylacrylates, acrylonitrile, butadiene, dicyclopentadiene, cyanoacrylates,isoprene, and propylene.

For the methods of the present invention, the useful water-solublephenylenediamine compositions will retain at least one “—NH” group foreffective polymerization inhibition. The effective amount of thewater-soluble phenylenediamine composition having at least one “—NH”group used in the methods of the present invention as a polymerizationinhibitor is that amount which is sufficient to affect inhibition ofpolymerization and will vary according to the conditions under which themonomer is synthesized, processed, and/or stored. There are severalfactors that will affect the amount of inhibitor that is required.Factors that will require an increase in the amount of inhibitor areincreased monomer concentration and increased temperature.

Generally, an effective concentration of the water-solublephenylenediamine compositions of the present invention will range fromabout 0.5 ppm to about 2000 ppm, more desirably from about 1 ppm toabout 50 ppm. The compositions may be used in many hydrocarbonprocessing steps where premature polymerization is likely to occurincluding hydrocarbon cracking processes, preheating, distillation,hydrogenation, extraction, etc, The water-soluble phenylenediaminecomposition may be added at a location upstream of these processlocations.

The water-soluble phenylenediamine compositions may be added to a waterstream, hydrocarbon stream or to a monomer composition alone, or afterfirst being premixed with a solvent. Where a premix of the water-solublephenylenediamine composition is desired, it may be first combined with asolvent such as water or an organic solvent including, but not limitedto methanol, ethanol, acetone, pyridine, nitrobenzene, n-hexadecane,n-hexane, methylene chloride, dimethyl sulphoxide, chloroform, carbontetrachloride, benzene, glycols, esters and ethers.

Other inhibitors or antifoulants known in the art may be combined withthe waters soluble phenylenediamine compounds of the present invention.These may include other phenylenediamines, hydroxylamines, nitroxides,and hindered phenols. When a compositions containing an additionalphenylenediamine composition is desired, the additional phenylenediaminemay correspond to the following formula:

wherein R^(a), R^(b) and R^(c) are independently selected from the groupconsisting of H, C₁-C₁₈ alkyl, hydroxyalkyl, —O—R⁶, —S—R⁶, —N—(R⁷)(R⁶),and aryl.

The water-soluble phenylenediamine compositions of the present inventionhave a wider variety of uses as compared to conventionalphenylenediamine inhibitors. For example, during processing ofacrylonitrile, there is contact with water and consequent fouling anddeposit formation in the water sections. A phenylenediamine compositionthat is not water-soluble will not be effective as an inhibitor in thissituation.

PDA's such as N-(1,4-dimethylpentyl)-N′-phenyl-p-phenylenediamine andN-(1,3-dimethylbutyl)-N-phenyl-p-phenylenediamine are not miscible withwater. Instead, when they are added to water, they separate, forming twodistinct layers, a PDA layer and a water layer. However, the PDA's ofthe present invention are completely miscible with water, When they areadded to water, the PDA's of the present invention do not form aseparate layer, i.e., a partition between the aqueous and hydrocarbonphases where it provides vinyl monomer free radical polymerizationinhibition.

The features and advantages of the present invention are more fullyshown by the following examples which are provided for purposes ofillustration and are not to be construed as limiting the invention inany way.

EXAMPLES

Acrylonitrile was chosen to represent reactive vinyl monomers. Thewater-soluble phenylenediamines (PDA's) of the present invention weretested in acrylonitrile. Comparative testing was also performed usingconventional polymerization inhibitors. The comparative inhibitorcompositions are shown in TABLE 1, while the inventive inhibitorcompositions which were tested are shown in TABLE 2. The parenthesisafter the inhibitor names indicates the weight ratio of two or moreinhibitors in the composition.

TABLE 1 Comparative Inhibitor Compositions Composition Inhibitor(s) ABlank B Hydroquinone C N-(1,3-dimethylbutyl)-N-phenyl-p-phenylenediamineD Benzoquinonediimide E Benzoquinonediimide/Hydroquinone (1:1) FHydroquinone/N-(1,3-dimethylbutyl)-N-phenyl-p- phenylenediamine (1:1) GHydroquinone/N-(1,4-dimethylpentyl)-N′-phenyl-p- phenylenediamine (1:1)H N-(1,4-dimethylpentyl)-N′-phenyl-p- phenylenediamine

TABLE 2 Inventive Inhibitor Compositions Composition Inhibitor(s) IN,N,N′,N′-Tetrahydroxypropylphenylenediamine JN-hydroxypropylphenylenediamine and N,N′-dihydroxypropylphenylenediamine (reaction mixture) KN-hydroxypropylphenylenediamine and N,N′-dihydroxypropylphenylenediamine (reaction mixture)/ Hydroquinone (1:1) LN-hydroxypropylphenylenediamine and N,N′-dihydroxypropylphenylenediamine (reaction mixture)/ Benzoquinonediimide(1:1)

For each of the experiments, acrylonitrile was heated under an inertatmosphere in glass tubes. A single inhibitor composition (A-L) wasadded to each tube. In the first experiment, tubes containingacrylonitrile were dosed with 2 ppm of various inhibitors and wereheated at 110° C.

For the second experiment, 35 ppm azobisobutyronitrile (AIBN), a freeradical polymerization initiator, was also added to each tube tosimulate conditions where fee radical concentrations are relativelyhigh. The second experiment was conducted at 66° C.

For each experiment, the performance of the inhibitor performance wasjudged by the length of the induction time for polymerization, i.e., theformation of visible polymer, as the reaction mixture turned turbid andwhite polyacrylonitrile started to deposit. The results of bothexperiments are shown in TABLE 3, below.

TABLE 3 Results of Acrylonitrile Study Induction Time to PolymerizationExperiment 2 (with polymerization initiator) Composition Experiment 1(hours) (minutes) A 1 15 B 2.2 132 C 106 n/a D 508 n/a E 528 160 F n/a183 G n/a 195 H n/a 230 I 4 49 J 106 290 K 168 n/a L 278 n/a

As can be seen from TABLE 3, the inventive compositions J, K and Lperformed better than the comparative compositions that included theknown polymerization inhibitors hydroquinone,N-(1,4-dimethylpentyl)-N′-phenyl-p-phenylenediamine, andN-(1,3-dimethylbutyl)-N-phenyl-p-phenylenediamine. In addition,inventive composition J has the advantage of being water-soluble whichincreases the variety of potential uses.

While there have been described what are presently believed to be thepreferred embodiments of the invention, those skilled in the art willrealize that changes and modifications may be made thereto withoutdeparting from the spirit of the invention, and it is intended toinclude all such changes and modifications as fall within the true scopeof the invention.

1.-10. (canceled)
 11. A composition resistant to polymerizationcomprising: (a) an ethylenically unsaturated monomer, and (b) one ormore water-soluble compounds of the following formula:

wherein at least one of R¹, R², and R³ is

R¹, R² and R³ are independently selected from H, C₁-C₁₈ alkyl,hydroxyalkyl, —O—R⁶, —S—R⁶, —N—(R⁷)(R⁸), aryl, and

R⁵ is selected from the group consisting of H, alkyl, hydroxyalkyl,—O—R⁶, —S—R⁶, —N—(R⁷)(R⁸), and aryl; Z comprises one or moresubstituents selected from the group consisting of hydrogen, alkyl,alkenyl, alkynyl, cycloalkyl, cycloalkenyl, aryl, heterocyclo, —CN,—NO₂, —O—R⁶, —S—R⁶, and —N(R⁷)(R⁸), R⁶, R⁷ and R⁸ are independentlyselected form the group consisting of hydrogen, alkyl, alkenyl, alkynyl,cycloalkyl, cycloalkenyl, aryl and heterocyclo; and wherein saidcomposition is water-soluble.
 12. The composition of claim furthercomprising a solvent. 13.-21. (canceled)